Italian Prime Minister Berlusconi struck in face at rally

Berlusconi taken to hospital; upper lip and cheek of the prime minister, 73, was bleeding

Berlusconi was at campaign rally in Milan for a local political ally

Rome, Italy (CNN) -- Italian Prime Minister Silvio Berlusconi will stay in a hospital for observation overnight after being hit in the face at a campaign rally in Milan, a spokesman said Sunday.

Milan police were questioning a man with a history of mental illness in connection with the attack, which left the 73-year-old Berlusconi bleeding profusely from his left upper lip and cheek. The premier underwent a CAT scan at Milan's San Raffaele Hospital, and his personal physician, Alberto Sangrillon, recommended more tests be done, Berlusconi spokesman Paolo Buonaiuti told CNN.

The conservative media-mogul-turned-politician has been dogged by allegations of corruption and is in the middle of a messy divorce from his second wife. He was in Milan, his hometown and political base, to stump for a local political ally.

Milan police said Berlusconi's attacker hit him with a small, metal souvenir replica of the Doumo di Milano, the city's central cathedral, but it was not immediately clear whether the man swung at the prime minister with the object in his hand or threw it at him.

Defense Minister Ignazio La Russa told the Italian newspaper Corriere della Sera that Berlusconi continued to shake hands with supporters for "a couple of minutes" after being hit.

"He remained calm and leaned out the window as he was being driven to the hospital and waved to the crowd," La Russa said.

Buonaiuti said there was "a lot of confusion" surrounding the assault, but he put some of the blame on Berlusconi's critics.

"What I can tell you is that there has been such a buildup of hatred toward the premier, and this is not good," Buonaiuti said. "This campaign of hatred has been building quite rapidly recently, and I am not surprised that what happened tonight took place."

But Milan police said the man being questioned in connection with the assault was a "mentally unstable" man in his early 40s who had been undergoing psychological treatment for some time. The man, identified as Massimo Tartaglia, is the only person arrested and is believed to have acted alone, they said.

The three-term prime minister faces trial on tax fraud charges after Italy's top court struck down an immunity law that shielded him from prosecution. He denies the charges, calling them politically motivated.

And his private life has been in the spotlight since his wife of 19 years, Veronica Lario, filed for divorce in May. The divorce followed allegations that an Italian businessman hired escorts for the premier and that he had attended the birthday party for an 18-year-old girl, with whom he has denied having an inappropriate relationship.

Berlusconi remains popular among the Italian public, however, with his approval ratings remaining well over 50 percent. He won a third term in 2008, and his conservative coalition has control of both the Italian Chamber of Deputies and the Senate.